Rotor for a charging device

ABSTRACT

A rotor for a charging device may include a shaft, a turbine wheel and a compressor wheel. The turbine wheel may be connected to the shaft. The rotor may also include at least one of a metal or ceramic adapter connected to the turbine wheel or the shaft via an infiltration process.

CROSS-REFERENCES TO RELATED APPLICATION

This application claims priority to German patent application DE 10 2010 011 486.3 filed on Mar. 16, 2010, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a rotor for a charging device, more preferably for an exhaust gas turbocharger, with a shaft carrying a turbine wheel and a compressor wheel according to the preamble of claim 1. The invention additionally relates to a charging device equipped with such a rotor. The invention additionally relates to a rotor for a charging device according to the preamble of claims 8 and 10.

BACKGROUND

From DE 10 2004 025 049 A1 a generic rotor is known, wherein the shaft between a turbine wheel and a mounting comprises at least one heat insulation whose heat permeability is lower than that of the regions of the shaft adjoining the heat insulation and which inhibits the heat passage through the shaft. The intention of this is to more preferably achieve an improved heat management.

From EP 1 002 935 A1 a further rotor is known wherein a turbine wheel via an adapter consists of a nickel or cobalt-based alloy. In order to be able to reduce an undesirable heat flow from the turbine wheel to a temperature-sensitive bearing guiding the steel body of the bearing shaft in the process, the adapter is constructed of at least two rigidly interconnected cylinder portions, of which one is formed of the nickel or cobalt-based alloy and another of a steel with a lower heat conductivity compared with the material of the steel body.

Further rotors are known for example from WO 2006/105891 A1 and from U.S. Pat. No. 4,557,704.

Finally, a rotor wherein a turbine wheel is screwed to a shaft via a thread is known from DE 10 2007 028 346 A1. Generally, turbine/compressor wheels are usually connected to a corresponding shaft by way of thermal joining methods, for example electron beam or friction welding or brazing. Here, the parts to be joined are solid and the parts are joined in a manufacturing step that is separate from the actual parts production. At the joining point of the turbine/compressor wheel with the shaft, however, a local, frequently sudden change of the material/structure properties and accompanied by this a component weakening occur. In addition to this, not all materials that are possible for a turbine/compressor wheel, particularly not with inter-metal phases, can be interconnected through fusion joining methods (beam welding/brazing).

SUMMARY

The present invention therefore deals with the problem of stating an improved or at least an alternative embodiment for a rotor of the generic type which more preferably does not have the disadvantages mentioned in the prior art.

According to the invention, this problem is solved through the subjects of the independent claims. Advantageous embodiments are the subject of the dependent claims.

The present invention is based on the general idea of providing at least one porous, metal or ceramic adapter between the shaft and the turbine wheel for connecting more preferably a turbine wheel to a shaft of a rotor, which adapter is connected to the turbine wheel and/or the shaft via an infiltration process. Here, the mentioned turbine wheel obviously also stands exemplarily for a compressor wheel that can be connected to the shaft in a similar manner. The porous adapter can either be connected to the shaft via infiltration, for example during a casting process of the turbine wheel or by a casting-on process or sintered onto the shaft or the turbine wheel in a sintering process in advance and subsequently connected to the respective second component through infiltration. Particularly in the case of a metal adapter, connecting the adapter to the turbine wheel or to the shaft through material joining, for example welding or brazing is also conceivable, wherein a connection to the second component is subsequently performed through infiltration. In general, the invention has the following advantages: joining of a shaft and a turbine wheel having totally different physical properties such as for example a thermal expansion coefficient is possible, wherein more preferably with conventional material joining, mechanically non-stable phases can form in the interface. Here, the adapter usually has a lower density than the turbine wheel or than the shaft so that a centre of gravity of the rotor is advantageously shifted in the direction of the compressor. Because of a suitable material configuration a heat wear resistance can also be increased in the region of radial shaft sealing rings. Of particular advantage however is that materials that could not be combined in the past can now also be joined together in a process-secure manner, that is fastened to one another, wherein in the joining region no sudden change of the material structure properties have to be feared which could lead to an undesirable component weakening in this region.

With an advantageous further development of the solution according to the invention the adapter is designed as metal adapter and materially connected to the shaft or the turbine wheel. This would open up the optional possibility of replacing one of the two infiltration processes, that is either the connecting of the adapter to the shaft or to the turbine wheel through conventional material connecting. Obviously, as an alternative to the material connecting, sintering onto one of the two components can also be chosen.

Further important features and advantages of the invention are obtained from the subclaims, from the drawings and from the corresponding figure description by means of the drawings.

It is to be understood that the features mentioned above and still to be explained in the following cannot only be used in the respective combination stated, but also in other combinations or standing alone, without leaving the scope of the present invention.

Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference characters refer to same or similar or functionally same components.

BRIEF DESCRIPTION OF THE DRAWING

It shows, in each case schematically,

FIG. 1 a rotor according to the invention with an adapter arranged between a shaft and a turbine/compressor wheel,

FIG. 2 a turbine wheel caulked to a shaft,

FIG. 3 a representation as in FIG. 2, however with another embodiment,

FIG. 4 a rotor with a conical shaft for improved radial alignment of a turbine/compressor wheel.

DETAILED DESCRIPTION

According to FIG. 1, a rotor 1 according to the invention comprises a shaft 3 carrying a turbine wheel 2 for a charging device which is not shown, more preferably for an exhaust gas turbocharger. Here, the turbine wheel 2 can obviously also stand analogously for a compressor wheel which is not designated in more detail. According to the invention, for connecting the turbine wheel 2 to the shaft 3 at least one porous metal or ceramic adapter 4 is now provided between said turbine wheel and the shaft 3, which adapter is connected to the turbine wheel 2 and/or to the shaft 3 via an infiltration process. The adapter 4 according to the invention can have an annular shape as is shown according to FIGS. 1 a and 1 b or a disc-like shape, as is drawn for example in FIG. 1 c. Compared with conventional connections of turbine wheels to corresponding shafts a transition between the turbine wheel 2 and the shaft 3 can be achieved with the rotor 1 according to the invention without sudden change of material/structure properties and thus without weak points that have been previously occurring there. The adapter 4 can for example be connected in/to the turbine wheel 2 during the casting process by means of infiltration and subsequently to the shaft 3 via a casting-on process. Alternatively it is also conceivable that the adapter 4 is sintered to the turbine wheel 2 or to the shaft 3. In this case the adapter 4 for example is connected to the turbine wheel 2 by means of a sintering process while the connection to the shaft 3 is established in a subsequent infiltration process.

In general it is also conceivable that the adapter 4 is designed as metal adapter 4 and initially in a first connecting step is materially connected to the shaft 3 or to the turbine wheel 2. Such a material connecting can be effected for example by means of welding or brazing. In a subsequent manufacturing step the adapter 4 is connected to the second component, i.e. for example to the turbine wheel 2 or the shaft 3 by means of infiltration process.

Considering FIG. 1 b, it can be seen that the adapter 4 is integrated, for example embedded in a back of the turbine wheel 2. With the rotor 1 produced according to the invention it is more preferably also possible to interconnect a turbine wheel 2 and a shaft 3 with totally different physical properties, for example thermal expansion coefficients, in a process-secure manner. Based on the fact that the adapter 4 usually has a lower density than the turbine wheel 2 or the shaft 3 a centre of gravity of the rotor 1 is advantageously also shifted in the direction of the compressor. The rotor 1 according to the invention can also be configured for optimum heat wear resistance of the rotor 1 in terms of material in the region of radial shaft sealing rings. Through the porous structure of the adapter 4 said adapter is infiltrated by a liquid material of said shaft/turbine wheel during the connecting process, as a result of which a particularly strong connection can be achieved. Connecting the shaft 3 to the composite of turbine wheel 2 and adapter 4 can be presented in the following manner: casting-on (infiltrating of a shaft material in a suitable device) or through local melting-on of the shaft material blank under axial pressure to the face end joining point. Obviously, the joining process shown can also be performed in reverse order so that initially casting-on or an infiltration of the adapter 4 to the shaft 3 takes place and this composite formed of adapter 4 and shaft 3 is subsequently used as insertion component in the casting process of the turbine wheel 2 and is infiltrated by the material of the turbine wheel 2.

Alternatively to the embodiment shown according to FIG. 1, webs 6 radially standing away to the outside can be arranged on the shaft 3 for connecting the turbine wheel 2 to the shaft 3, and/or webs 6′ radially standing away to the inside can be arranged on a receiving opening 5 of the turbine wheel 2, which are plastically deformed when the turbine wheel 2 is slid onto the shaft 3, as is for example shown in the right sectional representation in FIG. 2. The two sectional representations in this case are orientated orthogonally to the sectional figure of the rotor 1 with respect to a viewing plane. In the left sectional representation it can be seen that the webs 6′ are designed as longitudinal webs, wherein circumferential webs are obviously also conceivable. The webs 6′ in this case have a smaller projection ü, so that an outer diameter of the shaft 3 is larger than an inner diameter of the receiving opening 5. Here, caulking of the turbine wheel 2 with the shaft 3 results in a plastic deformation of the webs 6, 6′, as a result of which a positive and particularly sturdy connection can be achieved. In the upper sectional representation in FIG. 2 a region not yet caulked is marked with the reference character I, while the already caulked region is shown with the reference character II.

According to FIG. 2, the webs 6′ are arranged as webs 6′ on the turbine wheel 2 standing away radially to the inside, wherein according to FIG. 3 the webs 6 alternatively or additionally can also be provided on the shaft 3 as webs 6 radially standing away to the outside. In FIG. 3, too, the reference character II marks the already caulked and the reference character I the region not yet caulked.

Looking at FIGS. 2 and 3 once more it is clear that the forming processes of the webs 6, 6′ upon caulking of the turbine wheel 2 to the shaft 3 is dependent on the hardness of the two materials. Axially adjacent to the regions with the webs 6, 6′ a region 11 is provided at least on one end which has no webs 6 and because of this makes possible a coaxial alignment of the turbine/compressor wheel 2 on the shaft 3. A major advantage of this type of connection is that for connecting no additional operation such as screwing or welding is required. The webs 6, 6′ can have almost any shape, for example flutes, helicals, etc.

FIG. 4 shows a further alternative embodiment for connecting a turbine wheel 2 to a shaft 3, wherein the shaft in this case has a conically tapering region 7 with an outer thread 8 arranged on a free end of the shaft 3. On the turbine wheel 2, a conical receiving opening 9 designed complimentarily to the conical region 7 is provided, with an internal thread 10 following this, wherein through the conical configuration of the conical region 7 or the conical receiving opening 9 an exact radial alignment of the turbine wheel 2 can be achieved. In this case the term turbine wheel 2 obviously stands analogously for the connection of the invention to a compressor wheel. Obviously it is also conceivable that the outer thread 8 is located outside the turbine wheel 2, wherein in this case a nut is screwed onto the outer thread 8, which for improving the aerodynamic characteristics is covered with a suitable cap which is not shown. 

1. A rotor for a charging device comprising: a shaft, a turbine wheel and a compressor wheel, wherein the turbine wheel is connected to the shaft, at least one of a metal or ceramic adapter connected to the turbine wheel and the shaft via an infiltration process.
 2. The rotor according to claim 1, wherein the adapter is sintered onto at least one of the turbine wheel and the shaft.
 3. The rotor according to claim 1, wherein the adapter is a metal adapter and connected to at least one of the shaft and the turbine wheel.
 4. The rotor according to claim 3, wherein the adapter is welded to at least one of the shaft and the turbine wheel.
 5. The rotor according to claim 1, wherein the adapter has at least one of an annular shape and a disc-like-shape.
 6. The rotor according to claim 1, wherein the adapter is integrated in a back of the turbine wheel.
 7. The rotor according to claim 1, wherein the rotor is disposed in an exhaust gas turbocharger.
 8. A rotor for a charging device comprising: a shaft, a turbine wheel and a compressor wheel, the turbine wheel being connected to the shaft, a plurality of webs extending radially away to the outside of and arranged on the shaft, and longitudinal webs extending radially away to the outside of the shaft and being arranged on a receiving opening of the turbine wheel, the webs and longitudinal webs configured to deformed when the turbine wheel is slid onto the shaft.
 9. The rotor according to claim 8, wherein the webs are designed as at least one of the longitudinal webs and circumferential webs.
 10. A rotor for a charging device comprising: a shaft, a turbine wheel and a compressor wheel, a conically tapering region having an outer thread arranged on the free end of the shaft, wherein the turbine wheel has a conical receiving opening formed complementarily thereto with a following internal thread.
 11. The rotor according to claim 1, wherein the adapter is sintered onto the turbine wheel.
 12. The rotor according to claim 1, wherein the adapter is sintered onto the shaft.
 13. The rotor according to claim 1, wherein the adapter is a metal adapter and connected to the shaft.
 14. The rotor according to claim 1, wherein the adapter is a metal adapter and connected to the turbine wheel.
 15. The rotor according to claim 3, wherein the adapter is brazed to the shaft.
 16. The rotor according to claim 3, wherein the adapter is brazed to the turbine wheel.
 17. The rotor according to claim 1, wherein the adapter has an annular shape.
 18. The rotor according to claim 1, wherein the adapter has a disc-like-shape.
 19. The rotor according to claim 2, wherein the adapter has at least one of an annular and a disc-like-shape.
 20. The rotor according to claim 2, wherein the adapter is integrated in a back of the turbine wheel. 